The present invention relates to a power window driving apparatus for driving and controlling a power window installed in a vehicle, and more particularly to a technique for detecting with high accuracy a seizure of an obstacle when the obstacle seizure occurs at an initial stage of the driving of the power window.
A power window glass is connected to a driving motor and is operated to be raised or lowered by rotating reversibly the driving motor through operation of a switch. In addition, there has been proposed and put into practical use a power window having a function to prevent a damage to an obstacle and/or a power window glass that would be caused in the event that the obstacle is seized by the power window while it is being raised by stopping and then reversing the driving motor so as to lower the power window glass.
In the power window having the obstacle seizure preventing function, in the event that an obstacle seizure by the power window occurs immediately after the driving motor has been activated, it is not possible to detect the obstacle seizure momentarily, resulting in a case where an excessive load is applied to the obstacle.
Namely, when the driving motor is activated, a rush current flows, and the obstacle seizure detecting function does not work until the rush current disappears. In addition, when the window glass is operated to be raised after it has been lowered and stopped once, there is generated a state where no load is applied to the driving motor immediately after the raising operation has been implemented, and there exists a time period when the motor current becomes extremely small. Then, this time period has elapsed, a load is then applied to the driving motor, and the current flowing to the driving motor is increased drastically.
In the related power window driving apparatus, the drastic increase in the current is detected, and this results in an erroneous reversal of the driving motor in which the driving motor is erroneously stopped or reversed (see JP-A-2001-20605, for example).
As described above, in the related power window driving apparatus, in the event that the obstacle is seized by the window glass, since the seizure is detected and the window is then stopped or reversed, trouble in association with the obstacle seizure can be avoided, however, there still occurs a case where trouble takes place that the motor is erroneously stopped or reversed when the current develops again after the current has decreased after the motor was driven, and there has been developed a demand to prevent the occurrence of the trouble by some means or other.